JPH04272158A - Nonmagnetic stainless steel having low work hardenability - Google Patents

Abstract

PURPOSE:To provide a low-cost electronic member by using nonmagnetic stainless steel contg. a specified wt.% each of C, Si, Mn, P, S, Cr, Ni and N. CONSTITUTION:A compsn. contg. <=0.05% C, <=1.00% Si, 2.0-15.0% Mn, <=0.0045% P, <=0.03% S, 15.0-18.0% Cr, 9.0-15.0% Ni and <=0.05% N and ensuring <=60 deg.C Md 30 value and >=3.0 Ni balance is rendered to nonmagnetic stainless steel. The resulting steel can be subjected to multistage drawing without carrying out process annealing and the cold workability of the steel can be remarkably improved.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-magnetic stainless steel with low work hardening properties, and particularly to a soft non-magnetic stainless steel that can be drawn in multiple steps without intermediate annealing.

0002

BACKGROUND OF THE INVENTION Nowadays, as various electronic devices have become widespread, it has become necessary for electronic parts to be non-magnetic, and various materials and members have been used for such non-magnetic electronic parts. In order to exhibit excellent nonmagnetic effects, attempts have been made to improve the nonmagnetic properties of materials as well. Such electronic parts are often formed into a desired shape by severe deep drawing. For example, electronic components such as guide rollers of tape recorders are subjected to sophisticated processing with an aperture ratio of about 5. However, at present, when drawing is performed in multiple stages, an annealing step is added each time to soften the material, and then drawing is performed again. Due to work hardening, the annealing step cannot be omitted even if the material is processed in multiple stages.

For example, when producing a material with a drawing ratio of about 5 as shown in Table 4 by multi-step drawing, conventional SUS304 must be subjected to an annealing process of 1080° C. for 5 minutes at a drawing ratio of about 2.5. When considering supplying inexpensive electronic components in large quantities, such conventional methods are too expensive in terms of cost. JP-A-52-62113 discloses a steel type in which C+N is limited to 0.04 to 0.10 in order to improve press formability, but this steel type has an Md30 value of 14 to 33 and N
i-bal. is -0.5 to -2.5. Furthermore, JP-A-1-301840 also discloses an austenitic steel with reduced C+N;
d30 value is 11-18, Ni-bal. is -1.8
~-2.0. FIGS. 1 and 2 show Md30 values and Ni-bal. The relationship between n value and magnetism is shown below, but as is clear from this, both of the above two steel types become magnetic due to processing, and non-magnetism cannot be ensured. Therefore, they are essentially different from each other in terms of usage.

0004

SUMMARY OF THE INVENTION An object of the present invention is to provide a non-magnetic stainless steel with low work hardening properties, which can be easily manufactured into electronic components at low manufacturing cost.

[0005]

[Means for solving the problem] Non-magnetic stainless steel is a suitable material for electronic parts, but these do not have sufficient workability and require multiple intermediate annealing processes in severe forming such as deep drawing. Therefore, it was expensive in terms of cost. The present inventors conducted various studies to solve this problem, and found that the C and N contents were each reduced to 0.
By limiting the Md30 value, which is an indicator of the stability of the austenite phase, to -60℃ or less, it became possible to perform drawing in multiple steps without intermediate annealing. , completed the invention.

The gist of the present invention is that C
: 0.05% or less, Si: 1.00% or less, Mn:
2.0-15.0%, P: 0.0045% or less, S:
0.030% or less, Cr: 15.0 to 18.0%, N
i: 9.0-15.0%, Cu: 0-5.0%, N:
0.05% or less, Md30 value: -60°C or less, Ni-
It is a soft non-magnetic stainless steel having a composition of bal: 3.0 or more and capable of being drawn in multiple steps without intermediate annealing.

[0007]

[Operation] Next, the reason why the steel composition is limited as described above in the present invention will be explained. In this specification, "%" means "% by weight" unless otherwise specified. C, N: Generally, austenitic stainless steel produces deformation-induced martensite (α') through cold working. In that case, α' generated when a large amount of C and N is contained
becomes hard, and C and N are each added at 0.05% in order to improve the work hardening properties that are characteristic of the steel according to the present invention.
The following was made.

Si: Si is an element that has a deoxidizing effect, but if it is contained in a large amount, the material hardens, and since it is a ferrite-forming element, it impairs magnetism and hot workability.
．． 00% or less. Mn: Mn is an element necessary to stabilize the austenite phase at a low cost and to ensure nonmagnetism, and is set to 2.0 to 15.0% in combination with Ni and Cu.

[0009] P: If P exceeds 0.045%, corrosion resistance and hot workability deteriorate, so the upper limit is set at 0.045%.
%. S: If S exceeds 0.030%, inclusions increase, corrosion resistance deteriorates, and hot workability may be inhibited, so the upper limit was set at 0.030%.

Cr: Cr is the most effective element in ensuring the corrosion resistance of stainless steel, and for this purpose, it must be at least 13.0%, and in practice it is preferably 15%.
．． 0% or more is desired. However, if it exceeds 20.0%, ferrite formation and hot workability are inhibited, so it is preferably 18.0% or less. Therefore, the upper limit of Cr was set to 18.0%, and the lower limit was set to 15.0%.

[0011] Ni: Ni is the most effective element for stabilizing the austenite phase and ensuring non-magnetism, and to obtain these effects it must be 9.0% or more, depending on the combination with the amounts of Mn and Cu. is necessary. The higher the Ni content, the greater the effect, but since Ni is an expensive element, the upper limit was set at 15.0% in consideration of economic efficiency.

Cu: Cu exhibits the same effect as Ni and is an effective element for lowering the work hardening rate. Mn, Ni
Depending on the combination, it is not always necessary to add it, but it is preferably added up to 5.0%. However, 5.0
If added in excess of %, hot workability deteriorates.
When added, the upper limit was set at 5.0%.

Md30 value: Md30 value represents austenite stability and is defined by the following formula. Md30(℃)=497-462(C+N)
-9.2Si-8.1Mn-13.7Cr-20(Ni
+Cu)-18.5Mo As shown in FIG. 1, the higher the Md30 value, the higher the magnetism, and the higher the work hardening rate (n value). Therefore, Md
30 value needs to be -60°C or lower.

Ni-bal. :Ni-bal. represents the balance between austenite and ferrite phases,
In this specification, it is defined by the following formula. Ni-bal. = [Ni+30(C+N)+0
．． 5Mn+0.3Cu+8.2]-1.1(Cr+1.
5Si) As shown in FIG. As the value becomes smaller, a ferrite phase is generated, resulting in magnetism. Therefore, Ni-bal. must be 3.0 or higher.

In addition, in the present invention, P and S are contained as impurities of 0.045% or less and 0.030%, respectively.
However, if P exceeds 0.045%, corrosion resistance and hot workability will deteriorate, and if S exceeds 0.030%, inclusions will increase and corrosion resistance will deteriorate. This is because hot workability may be inhibited. Next, the present invention will be explained in more detail with reference to Examples.

[0016]

[Example 1] Test steel having the steel composition shown in Table 1 was melted and subjected to conventional continuous casting, hot rolling, and cold rolling to produce cold rolled steel plates (thickness 0.6 mm). In addition to evaluating the mechanical properties, drawing forming was performed to evaluate the workability. The magnetic material is 0.6mm thick and 80mm in diameter.
These are the values measured with a ferrite scope for a disk formed by deep drawing into a cylindrical body with a diameter of 15 mm and a height of 100 mm. However, for conventional steel and comparative steel where cracks occurred in the middle of the process, the values were measured in the process before the cracks occurred.

The results are summarized in Tables 2 and 3. As can be seen from these results, according to the present invention, the predetermined component range is satisfied, and the Md30 value is -60°C or less.
Ni-bal. By making n more than 3.0
The value can be lowered to make it non-magnetic. On the other hand, the conventional steel No. 11 (SUS304 steel), the component range, Md30 value, and Ni-bal. Both n-value and magnetism are high because both are not satisfied, and steel No. 1 is used as a comparative example. 12 and 13 satisfy the component range, but the Md30 value and Ni-bal. Since one of these is not satisfied, the n value and magnetism are high.

[0018]

[Example 2] Steel No. in Table 1. 4, 6, 7, 10,
Steel No. 11 (conventional example), Steel No. 12 (Comparative example)
For each, the thickness is 0.6 mm and the diameter is 80 mm.
A cylindrical body with a diameter of 15 mm and a height of about 100 mm was deep drawn in multiple steps using a disk-shaped test piece. In the example of the present invention, processing was possible without intermediate annealing, but in both the conventional example and the comparative example, cracks occurred during the process, and intermediate annealing had to be performed. The results are shown in Table 4.

[0019]

[Table 1]

[0020]

[Table 2]

[0021]

[Table 3]

[0022]

[Table 4]

[0023]

[Effects of the Invention] As explained above, according to the present invention, the cold workability is significantly improved, and even during deep drawing, there is no need for intermediate annealing treatment. The present invention has great practical significance, as it enables the provision of inexpensive electronic components that are highly sought after today.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between Md30 value, n value, and magnetism.

FIG. 2 Ni-bal. It is a graph showing the relationship between n value and magnetism.

Claims (2)

[Claims] [Claim 1] C: 0.05% or less, Si: 1.00% or less, Mn in weight %
: 2.0-15.0%, P: 0.0045% or less, S
: 0.030% or less, Cr: 15.0 to 18.0%,
Ni: 9.0 to 15.0%, N: 0.05% or less, M
A soft non-magnetic stainless steel having a composition of d30 value: -60°C or less and Ni-bal: 3.0 or more, which can be drawn in multiple steps without intermediate annealing. 2. The non-magnetic stainless steel according to claim 1, further containing Cu: 5.0% or less.